REV. 0

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

Low Voltage, Resistor Programmable

Thermostatic Switch

AD22105

© Analog Devices, Inc., 1996

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 617/329-4700

Fax: 617/326-8703

FEATURES

User-Programmable Temperature Setpoint

2.0 C Setpoint Accuracy

4.0 C Preset Hysteresis

Wide Supply Range (+2.7 V dc to +7.0 V dc)

Wide Temperature Range (–40 C to +150 C)

Low Power Dissipation (230

W @ 3.3 V)

APPLICATIONS

Industrial Process Control

Thermal Control Systems

CPU Monitoring (i.e., Pentium)

Computer Thermal Management Circuits

Fan Control

Handheld/Portable Electronic Equipment

The AD22105 is designed to operate on a single power supply

voltage from +2.7 V to +7.0 V facilitating operation in battery

powered applications as well as in industrial control systems.

Because of low power dissipation (230

µW @ 3.3 V), self-

heating errors are minimized and battery life is maximized.

An optional internal 200 k

Ω pull-up resistor is included to

facilitate driving light loads such as CMOS inputs.

Alternatively, a low power LED indicator may be driven directly.

GENERAL DESCRIPTION

The AD22105 is a solid state thermostatic switch. Requiring

only one external programming resistor, the AD22105 can be set

to switch accurately at any temperature in the wide operating

range of –40

°C to +150°C. Using a novel circuit architecture,

the AD22105 asserts an open collector output when the ambient

temperature exceeds the user-programmed setpoint temperature.

The AD22105 has approximately 4

°C of hysteresis which prevents

rapid thermal on/off cycling.

FUNCTIONAL BLOCK DIAGRAM

1

2

3

4

8

7

6

5

NC

NC

OUT

GND

NC

TEMPERATURE

SENSOR

200k

Ω

SET–

POINT

AD22105

12

3

4

8

7

65

OUT

+2.7V TO +7.0V

AD22105

TOP VIEW

Figure 1. Typical Application Circuit